I wrote the library to render fonts in mobile phone games. I've used the library myself in apps that have been downloaded millions of times, not to mention apps made by others (which I don't have much information on). The heavy use means that the library has been battle-tested fairly well and is very efficient.
I periodically update FTGLES but it has mostly been superseded by DiFont which has better shader support.
See the Demos folder for several comprehensive sample iPhone apps. The demo apps include a unicode demo, as well as a demonstration of how to use layouts to easily align and position text.
"Unlike other OpenGL font libraries FTGL uses standard font file formats so doesn't need a preprocessing step to convert the high quality font data into a lesser quality, proprietary format."
"FTGL uses the Freetype font library to open and 'decode' the fonts. It then takes that output and stores it in a format most efficient for OpenGL rendering."